One example of EL display devices is an organic EL display device making use of electro-luminescence in organic materials. A top-emission type organic EL display device includes, for example, a pixel electrode formed on a substrate, and a hole injection layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, and a common electrode stacked on the pixel electrode. In the organic EL display device having such a structure, in order to prevent voltage drop produced in the common electrode with increasing size of a screen of the device, auxiliary wiring electrically connected to the common electrode is formed in a region, above the substrate, in which the pixel electrode is not formed (Patent Literature 1).
In a process of forming the layers of the above-mentioned organic EL display device, for example, the pixel electrode and the auxiliary wiring, which are made of an alloy of Al and Ag, are formed by sputtering, the hole injection layer, which is made of transition metal oxide, is also formed by sputtering, the hole transport layer and the organic light-emitting layer, which are made of a polymeric material, are formed by printing, the electron transport layer, which is made of a low-molecular material, is formed by evaporation, and the common electrode, which is made of transparent metal oxide such as indium tin oxide (ITO), is also formed by evaporation or sputtering. Further, the pixel electrode, which is formed for each pixel, and the hole transport layer and the organic light-emitting layer, which are formed by printing, are patterned, whereas the hole injection layer, the electron transport layer, and the common electrode are formed as a continuous film, or a so-called “solid film”, without being patterned, as there is no need to form these layers for each pixel, and it is not easy to pattern these layers formed by evaporation and sputtering with high precision. By thus omitting patterning, a manufacturing process has been simplified.